This application corresponds to Japanese Patent Application No. 10-94517, filed on Apr. 7, 1998, which is hereby incorporated by reference in its entirety.
1. Field of the Invention
The present invention relates to a feeder and feeding technique for feeding electronic chip components, and more particularly, to a feeder and feeding technique for feeding a plurality of randomly oriented electronic chip components in an aligned state.
2. Description of the Related Art
Feeders can be used for aligning and feeding a plurality of randomly oriented electronic chip components (such as capacitors, resistors, transistors, and filters). FIG. 4 schematically illustrates one related feeder for feeding electronic chip components. The feeder 1 shown there for feeding electronic chip components includes a retaining section 2, an aligning section 3, a conveying section 4, and a dispensing section 5, as respective functional sections.
The retaining section 2 includes a hopper 7 for retaining a plurality of electronic chip components 6 (illustrated in aggregate) in a randomly oriented state. A discharge opening 8 is formed in the bottom of the hopper 7. The aligning section 3 is associated with the discharge opening 8.
FIG. 5 is a cut-away perspective view showing the aligning section 3. As indicated there, an aligning path forming member 10 for forming a tubular aligning path 9 is disposed in the aligning section 3. The aligning path forming member 10 is placed inside the discharge opening 8, and reciprocates in the axial direction of the discharge opening 8 with a predetermined stroke 11 (or xe2x80x9cstroke rangexe2x80x9d), as indicated by solid lines and dotted lines in FIG. 5. This allows the aligning path forming member 10 to agitate electronic chip components 6, which are to be discharged from the discharge opening 8. Only the electronic chip components 6 oriented in a predetermined direction by this agitation are received into the aligning path 9.
In the aligning section 3 shown in FIG. 5, a fixed pipe 12 for guiding the electronic chip components 6 in an aligned state can be further provided within the tubular aligning path 9 of the aligning path forming member 10. This fixed pipe 12 serves to enable very small electronic chip components 6 to be handled. The inner diameter of the fixed pipe 12 is selected so as to receive an electronic component 6 only when the longitudinal direction of the electronic chip component 6 agrees with the axial direction of the fixed pipe 12.
As described above, the aligning path forming member 10 agitates the electronic chip components 6, by reciprocating movement thereof so as to smoothly move the electronic chip components 6 in the hopper 7, and to guide them to the aligning path 9 or the fixed pipe 12. In order to more smoothly guide the electronic chip components 6 to the aligning path 9 or the fixed pipe 12, a conical concave surface is formed on an end surface 13 located within the hopper 7 of the aligning path forming member 10.
Referring again to FIG. 4, the electronic chip components 6 which have passed through the aligning path forming member 10 or, more specifically, through the fixed pipe 12, arrive at the conveying section 4. In the conveying section 4, a conveying path 14 provided by, for example, a conveyor belt (not shown), is formed. The conveying path 14 conveys the electronic chip components 6 passing through the fixed pipe 12 in an aligned state.
The dispensing section 5, is formed at the end of the conveying path 14. In the dispensing section 5, a dispensing mechanism (not shown) is disposed for dispensing the electronic chip components 6. A device, such as a vacuum chuck, for picking up the electronic chip components 6, can be used as the dispensing mechanism.
In the feeder 1 for electronic chip components as described above, the number of the electronic chip components 6 guided into the aligning path 9 or the fixed pipe 12 per unit of time is usually set to be larger than the number of the electronic chip components 6 dispensed in the dispensing section 5 per unit of time. Therefore, a number of electronic chip components 6 are retained in the conveying path 14 so that the electronic chip components 6, which are to be dispensed, are not depleted from the dispensing section 5.
As described above, since the aligning path forming member 10 agitates the electronic chip components 6 by reciprocating movement thereof so as to guide the components into the aligning path 9 or the fixed pipe 12, one to more electronic chip components 6 should ideally be guided into the fixed pipe 12 in each cycle of the reciprocating movement of the aligning path forming member 10 without any interruption.
However, while the aligning path forming member 10 performs its reciprocating movements, a phenomenon may occur, as observed by the present inventors, in which the electronic chip components 6 fail to be guided into the aligning path 9 or the fixed pipe 12. For example, when 50,000 electronic chip components 6, each having the dimensions of 1.0xc3x970.5xc3x970.5 mm, are placed into the hopper 7, and when the number of the electronic chip components 6 remaining in the hopper 7 decreases to less than 10,000, the electronic chip components 6 are often not smoothly guided into the aligning path 9 or the fixed pipe 12.
FIG. 6 illustrates this phenomenon. In FIG. 6, the vertical axis represents the guiding-capacity corresponding to the number of the electronic chip components 6 to be guided into the aligning path 9 per reciprocating cycle of the aligning path forming member 10, and the horizontal axis represents the number of electronic chip components remaining in the hopper 7. It is observed that high guiding capacity is obtained when the remaining number of electronic chip components 6 is relatively large, such as xe2x80x9cR1xe2x80x9d or more, but the guiding capacity is reduced when the remaining number is less than xe2x80x9cR1,xe2x80x9d and decreases to xe2x80x9cR2xe2x80x9d and xe2x80x9cR3.xe2x80x9d
As discovered by the present inventors, the indicated curve may vary with the dimensions of each electronic chip component 6 and the length of the stroke 11. When each electronic chip component 6 has the dimensions of 1.0xc3x970.5xc3x970.5 mm and the stroke 11 is 12 mm, xe2x80x9cR1xe2x80x9d is 10,000, xe2x80x9cR2xe2x80x9d is 5,000, and xe2x80x9cR3xe2x80x9d is 3,000. When the remaining number of electronic components 6 decreases to about 3,000, the guiding capacity is significantly reduced.
One reason for the reduction in the guiding capacity may be as follows. That is, when a small number of electronic chip components 6 remain in the hopper 7, the electronic chip components 6 jump in the hopper 7 due to the reciprocating movement of the aligning path forming member 10 and the lack of a large number of other electronic chip components 6 to dampen their movements, preventing them from entering into the aligning path 9 or the fixed pipe 12. In addition, the existence of only a small number of electronic chip components 6 in the hopper 7, to the extent that they are tossed by the reciprocating movement of the aligning path forming member 10, means the probability of the electronic chip components 6 being near the discharge opening 8 is low, and hence, there is a reduced opportunity for the electronic chip components 6 to be guided into the aligning path 9 of the aligning path forming member 10 or the fixed pipe 12 due to the effects of gravity.
In order to prevent the reduction in the aforementioned guiding capacity, new electronic chip components 6 may be added to the hopper 7 so that the number of electronic chip components 6 remaining in the hopper is not reduced to less than 10,000, for example. In this case, however, the following problems are encountered.
The electronic chip components 6 of different lots may be mixed into one hopper 7. That is, some of the electronic chip components 6 remain in the hopper 7 before adding the new batch. Hence, a significant number of the electronic chip components 6 may become mechanically damaged, reducing the quality thereof, because they are impacted by the aligning path forming member 10 for a long period of time.
In order to avoid the above-mentioned problem, even if thousands of electronic chip components 6 remain in the hopper 7, the fresh electronic chip components 6 can be placed into the hopper 7 after removing the remaining (xe2x80x9coldxe2x80x9d) electronic chip components 6 when the above-mentioned guiding capacity is reduced. In this case, however, thousands of electronic chip components 6 will be wasted, and a relatively long period of time is required to replace the electronic chip components 6 to be pooled in the hopper 7.
Accordingly, it is an object of the present invention to provide a feeder and feeding technique for feeding electronic chip components which can maintain the guiding capacity for feeding electronic chip components into an aligning path of an aligning path forming member at a level higher than a predetermined level, regardless of the number of electronic chip components remaining in the hopper.
In accordance with an aspect of the present invention, a feeder is provided for feeding electronic chip components, including a hopper for retaining a plurality of electronic chip components. The hopper has a discharge opening formed in the bottom thereof. The feeder also includes an aligning path forming member located within the discharge opening for agitating electronic chip components by its reciprocating movement in the axial direction of the discharge opening. The aligning path forming member also forms a tubular aligning path which receives therein only the electronic chip components aligned in a predetermined direction. A conveying path is provided for conveying the electronic chip components which have passed through the aligning path forming member in an aligned state, and a mechanism for dispensing electronic chip components is provided at the end portion of the conveying path. According to a particularly advantageous feature, the reciprocating stroke range of the aligning path forming member can be varied.
More specifically, the stroke range of the aligning path forming member may preferably be controlled to be shortened when the number of electronic chip components remaining in the hopper is reduced. The stroke range can be shortened one or more times, or on a continuous basis. The stroke range of the aligning path forming member may preferably be reduced at least once when the number of electronic chip components remaining in the hopper is reduced to about one-fifth or less of the capacity of the hopper.
The feeder may further include a fixed pipe for guiding electronic chip components in an aligned state, the fixed pipe being disposed within the tubular aligning path of the aligning path forming member. In addition, the feeder can employ a conical concave surface formed on an end face located within the hopper of the aligning path forming member.